1. Field of the Invention
The present invention relates to an apparatus and method for controlling a linear compressor, which can prevent a piston of the compressor from colliding with a valve of the compressor, thereby improving the efficiency of operation of the compressor.
2. Description of the Related Art
FIG. 1 is a block diagram showing a conventional apparatus for controlling a linear compressor.
Referring to FIG. 1, the conventional control apparatus comprises a core 10 made of magnetic material and operated in conjunction with an object of detection, first and second coils 12 and 13 symmetrically wound around the core 10, and a signal processing unit 20 for detecting a change in the position of the core 10 using voltages induced to the first and second coils 12 and 13 and outputting the detected change.
The signal processing unit 20 comprises a first full-wave rectification unit 21 for full-wave rectifying a voltage induced in the first coil 12, a second full-wave rectification unit 22 for full-wave rectifying a voltage induced in the second coil 13, a differential amplification unit 23 for performing differential amplification by a difference between the voltages full-wave rectified by the first and second full-wave rectification units 21 and 22, a filter unit 24 for removing high-frequency components from a signal outputted from the differential amplification unit 23, and a peak detection unit 25 for detecting the highest and lowest values of a signal outputted from the filter unit 24 and transmitting the highest and lowest values to a microcomputer 30.
The operation of the conventional control apparatus is described below.
If the position of the core 10 is changed by a change in the position of the object of detection while alternating current with a frequency of several KHz is applied to the first and second coils 12 and 13, voltage proportional to the change in the position of core 10 is induced in the first and second coils 12 and 13. The voltage induced in the first and second coils 12 and 13 is full-wave rectified in the first and second full-wave rectification units 21 and 22, respectively, and inputted to the respective input terminals of the differential amplification unit 23.
The differential amplification unit 23 performs differential amplification by a difference between the voltages full-wave rectified by the first and second full-wave rectification units 21 and 22, and outputs an amplified signal to the filter unit 24. The filter unit 24 removes high-frequency components from the signal outputted from the differential amplification unit 23, amplifies the signal with the high-frequency components removed and outputs the amplified signal with the high-frequency components removed to the peak detection unit 25. The peak detection unit 25 full-wave rectifies the signal outputted from the filter unit 24 and outputs the rectified signal to the microcomputer 30. The microcomputer 30 controls the stroke of the linear compressor according to the full-wave rectified signal outputted from the filter unit 24.
The conventional linear compressor controlling apparatus can keep its stroke constant by controlling only the stroke detected by a sensor or the like. However, the center position of a piston of the linear compressor is changed according to load, therefore a constant top clearance of the piston cannot be maintained with respect to the top dead center of the piston. As a result, a problem arises that the piston of the linear compressor collides with the valve of the linear compressor.